🧪 Total carbon, hydrogen and nitrogen in hard coal, brown coal and coke — simultaneous combustion in oxygen and instrumental gas analysis (CO2, H2O, N2), ISO 29541

Petrochemistry ISO 29541

Overview

WHAT THE STANDARD COVERS. We have a preview of ISO 29541:2010 (first edition, title "Solid mineral fuels — Determination of total carbon, hydrogen and nitrogen content — Instrumental method") — from the table of contents to 8.4 (page 3 of 10). Most laboratories cite the second edition, ISO 29541:2025, whose text we did not have; we know as much about it as the ISO page gives (title "Coal and coke — …", 10 pages, February 2025, abstract) — which is why every number below is given as a number of the 2010 edition. Scope (Clause 1 of the 2010 edition): determination of total carbon, hydrogen and nitrogen in coal and coke by instrumental methods; note: the standard has been validated according to the principles of ISO 5725-1 for coal only. The abstract of the 2025 edition on the ISO page repeats the scope and adds that the interlaboratory study did not include coke, so there are insufficient data to state precision limits for coke. Foreword of the 2010 edition: it was prepared by ISO/TC 27/SC 5 and replaced ISO/TS 12902:2001 after a technical revision.

PROCEDURE (Clauses 4–8 of the preview). Carbon, hydrogen and nitrogen are determined concurrently: combustion of the sample in oxygen at elevated temperature converts them into CO2, H2O and N2/NOx, combustion products that would interfere are removed, nitrogen oxides are reduced to N2, and CO2, water vapour and nitrogen are measured by instrumental gas analysis. Carrier gas — helium or another gas specified by the instrument manufacturer, oxygen and additional reagents — as specified by the manufacturer. Calibration materials (Table 1, stoichiometric C / H / N contents in %): EDTA 41.1 / 5.5 / 9.6; phenylalanine 65.4 / 6.7 / 8.5; acetanilide 71.1 / 6.7 / 10.4; BBOT 72.5 / 6.1 / 6.5 — with a certificate stating uncertainty the certificate values are used, with purity > 99.5 % the stoichiometric ones; the interlaboratory study showed that benzoic acid is not suitable for calibration. Coals of certified composition serve only to check the instrument response and the nitrogen results, never for calibration, because the composition of coal changes during storage. The instrument is to analyse a test portion of 6 mg or more, and the balance must have a resolution of at least 0.1 % of the test portion. Sample — general analysis test sample with a nominal top size of 212 µm, prepared according to ISO 13909-4 (coal), ISO 13909-6 (coke), ISO 18283 or ISO 5069-2 (brown coals and lignites); moisture is determined according to ISO 11722, ISO 687 or ISO 5068-2, or the sample is dried before analysis. Blank analyses of the gases are made daily — nitrogen in the gases must not exceed 1 % of the nitrogen response for the lowest mass of calibration material. Stability: four determinations of a conditioning sample, the first discarded; if the largest difference of the remaining three exceeds 1.2 r (r — repeatability limit from Clause 10), instrument stability is suspect. Calibration — as recommended by the manufacturer, after changes to the instrument and when verification shows an unacceptable difference.

STATUS (state on 29 September 2026). ISO page: ISO 29541:2025, edition 2, published in February 2025, 10 pages, stage 90.92 "to be revised" — ISO/CD 29541 is in preparation; ISO 29541:2010 — withdrawn and replaced by the 2025 edition. The collection of Polish Standards does not contain this standard: the PKN search for "29541" and "ISO 29541" returns "No search results" (a check with the same query shape for "PN-EN ISO 23210" gives a result). The predecessor, ISO/TS 12902:2001, has a Polish edition PKN-ISO/TS 12902:2007, cited by 6 laboratories (AB 079, AB 103, AB 300, AB 550, AB 949, AB 1913) — the PKN card of this standardization document has no "Withdrawn" header (published 14-06-2007, 13 pages, KT 220 for Natural Solid Fuels, "Introduces: ISO/TS 12902:2001 [IDT]"), although in ISO the specification was replaced by ISO 29541:2010.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation-scope database, data loaded up to 17 September 2026, read on 29 September 2026). All notations of the number 29541: 30 entries at 11 laboratories (in the current PCA documents — 31: the database copy lacks the hydrogen entry of AB 103, see below). The 2025 edition — "ISO 29541:2025" (AB 300, AB 313, AB 786, AB 1120, AB 1833) and "ISO 29541:2025-02" (AB 081, AB 103, AB 688, AB 713, AB 1091); the withdrawn 2010 edition — AB 883. The "Laboratories" tab searches for notations BEGINNING WITH "ISO 29541" and shows 9 laboratories — checked with the tab query on the labcoda.pl production server on 29 September 2026: 9; AB 081 and AB 103 write the standard after PN-G-04571:1998 in one string and the tab does not show them. Current scopes on the PCA website (read on 29 September 2026, issues from 20.11.2025 to 08.09.2026): all entries stand in the valid issues, every pair of range limits from the copy appears in the current document and no entry is suspended (suspension footnotes in the scope of AB 103 concern other entries); the other way round (entries of the PCA documents with the number 29541 against the copy), one is missing from the copy: AB 103 has in its current scope (issue 42 of 18.02.2026, page 8) a separate hydrogen entry with this standard.

SUBJECT, TECHNIQUE AND RANGES. Hard coal — all 11 laboratories; brown coal — AB 081 and AB 103; coke from hard coal — AB 081, AB 103 (also semi-coke), AB 300 and AB 313; "processed solid fuels" — AB 081 and AB 103; petroleum coke — AB 313 (only by this standard). Elements determined: total carbon — 11 laboratories, hydrogen — 10 (without AB 1833; the hydrogen entry of AB 103 — (0.10 – 6.00) %, hard and brown coal, coke and semi-coke from hard coal, together with PN-G-04571:1998 and PKN-ISO/TS 12902:2007 — is in the current PCA document, but the database copy and labcoda.pl (read on 30 September 2026) do not have it), nitrogen — 6 (AB 313, AB 688, AB 713, AB 786, AB 883, AB 1120). Technique: "high-temperature combustion with IR detection" for carbon and hydrogen, "with TC detection" (thermal conductivity) for nitrogen. Ranges: carbon from (10.0 – 90.0) % (AB 688) and (20.0 – 100) % (AB 081) to (83.9 – 99.2) % (AB 313, petroleum coke); hydrogen from (0.01 – 8.00) % (AB 081) to (3.60 – 6.00) % (AB 1091); nitrogen from (0.03 – 2.20) % (AB 313) to (0.70 – 3.70) % (AB 1120).

ALONGSIDE THIS STANDARD. All 11 laboratories also have PN-G-04571:1998 in their scope — the Polish standard for determining carbon, hydrogen and nitrogen with automatic analysers (macro method), described in a separate Knowledge Base entry; it stands in the same entries as ISO 29541 at AB 081, AB 103, AB 300, AB 313, AB 688 and AB 883. PN-G-04571 is cited by 55 laboratories in total. PKN-ISO/TS 12902:2007 stands in the same entries at AB 103 and AB 300.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. Calibration: benzoic acid, although a typical elemental-analysis standard, is according to the interlaboratory study of the standard not suitable for it, and coal of known composition must not be used for calibration — only for checks. Coke: the standard is validated for coal, and the abstract of the 2025 edition says outright that there are no precision data for coke; the repeatability and reproducibility limits for coal cannot therefore be transferred to coke. Basis of the result: the analysis sample is tested with separately determined moisture or after drying; a result without the stated basis (as analysed, dry) is ambiguous.

WHAT WE DO NOT GIVE. We did not have the text of the 2025 edition, and the preview of the 2010 edition ends at 8.4 — we do not give the verification of calibration (8.5), the analysis of test samples (8.6), the expression of results (Clause 9), the repeatability and reproducibility limits (Clause 10) or the calibration recommendations of Annex A; we do not know what the 2025 edition changed apart from the title and the sentence about coke in the abstract.

Method principle

A test portion of the analysis sample of coal or coke (at least 6 mg according to the 2010 edition) is burnt in a stream of oxygen at high temperature. Carbon becomes CO2, hydrogen H2O, nitrogen N2 and nitrogen oxides; interfering products are removed and nitrogen oxides are reduced to N2. The gases are carried by helium (or another carrier gas specified by the manufacturer), and CO2, H2O and N2 are measured by instrumental gas analysis — in the laboratories' scopes, infrared detection for carbon and hydrogen and thermal-conductivity detection for nitrogen. The instrument is calibrated with pure compounds of known composition, and reference coals are used only for checks. Calculation and precision are in Clauses 9–10, beyond our preview.

Applications

• Elemental analysis of hard and brown coal and of coke — total carbon, hydrogen, nitrogen; in the scopes of 11 laboratories
• Data for combustion calculations and for carbon accounting (introduction of the standard: "carbon accounting")
• Petroleum coke — AB 313 only; the standard names coal and coke, and precision was determined for coal

Key parameters

Standard

Standard number

ISO 29541:2025 (Coal and coke — Determination of total carbon, hydrogen and nitrogen — Instrumental method); w zbiorze PN brak odpowiednika (stan wyszukiwarki PKN na 29.09.2026)

Title (PL)

Węgiel i koks — Oznaczanie węgla całkowitego, wodoru i azotu — Metoda instrumentalna (tytuł wydania 2025; nasze tłumaczenie)

Title (EN)

Coal and coke — Determination of total carbon, hydrogen and nitrogen — Instrumental method

Step-by-step procedure

1. Preparing the sample

   General analysis test sample 212 µm; moisture determination (ISO 11722, ISO 687 or ISO 5068-2) or drying before analysis.

2. Preparing the instrument

   Parameters according to the manufacturer's manual, condition and quantity of the reagents, leak-tightness of the combustion and carrier-gas system.

3. Blank analyses

   Daily and after changing gases or reagents; nitrogen in the gases ≤ 1 % of the response for the lowest calibrant mass.

4. Conditioning and stability

   Four determinations of a conditioning sample of composition typical of the samples, the first discarded; a difference of the remaining three above 1.2 r — corrective action before calibration.

5. Calibration

   According to the manufacturer, after changes to the instrument and when verification shows an unacceptable difference; pure compounds from Table 1, not benzoic acid and not coals.

6. Analysis and result

   Verification of calibration, analysis of samples, calculation and precision — 8.5–10, beyond the preview; we DO NOT GIVE them.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The analyser works with oxygen and at high temperature; helium and oxygen cylinders under pressure — follow the instrument manufacturer's rules
• SUBSTANTIVE NOTE: the standard is validated for coal; there are no precision data for coke (abstract of the 2025 edition on the ISO page)

Frequently asked questions